Ottawa weather in September
September is one of the best months to visit Ottawa: highs of 21°C (71°F) and about 87 mm (3.4 in) of rain on average. Nights average 10°C (50°F) and cloud cover 54% (NASA POWER, 2001–2025 averages). It is the 5th wettest month of the year and the 4th warmest. Compared with August, it is cooler and about as wet; October brings highs of 13°C (55°F) and 99 mm (3.9 in) of rain.
Is September a good time to visit Ottawa?
best month Weather score 75/100.
Yes. September is one of the best months for weather in Ottawa.
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Does it rain a lot in Ottawa in September?
Some rain is normal: about 87 mm (3.4 in) falls in an average September. It is the 5th wettest month of the year.
How warm is Ottawa in September?
Days average 21°C (71°F) and nights 10°C (50°F).
Ottawa weather by month
| Month | High | Low | Rain | Cloud | Weather |
|---|---|---|---|---|---|
| January | -6°C (20°F) | -16°C (3°F) | 61 mm | 70% | least pleasant |
| February | -5°C (23°F) | -15°C (4°F) | 55 mm | 67% | least pleasant |
| March | 2°C (35°F) | -9°C (16°F) | 64 mm | 64% | least pleasant |
| April | 11°C (51°F) | -1°C (31°F) | 85 mm | 65% | fair |
| May | 19°C (65°F) | 7°C (44°F) | 85 mm | 64% | best |
| June | 23°C (74°F) | 12°C (54°F) | 104 mm | 61% | best |
| July | 26°C (78°F) | 15°C (60°F) | 98 mm | 56% | best |
| August | 25°C (77°F) | 14°C (58°F) | 88 mm | 56% | best |
| September | 21°C (71°F) | 10°C (50°F) | 87 mm | 54% | best |
| October | 13°C (55°F) | 3°C (38°F) | 99 mm | 68% | fair |
| November | 5°C (41°F) | -3°C (27°F) | 73 mm | 72% | least pleasant |
| December | -3°C (27°F) | -11°C (12°F) | 80 mm | 76% | least pleasant |
Sources: 2001–2025 monthly averages from NASA POWER (MERRA-2 reanalysis). Page updated . How we rate months
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